Pruning tool



Nov. 8, 1955 R. L. HUBBARD PRUNING TOOL 2 Sheets-Sheet 1 Filed March 18,1955 l l l I I WM. 51!

INVEN TOR. F055 1. M49 5422 Nov. 8, 1955 R. L. HUBBARD 2,722,746

PRUNING TOOL Filed March 18, 1955 2 Sheets-Sheet 2 1 W W P J w my Qm Q QL M v r v; H mm N 7 R w m\ hm wm w United States Patent PRUNING TOOLRobert L. Hubbard, Florham Park, N. J.

Application March 18, 1955, Serial No. 495,119

Claims. (Cl. 30-180) This invention relates to devices for one-strokecutting of small limbs and the like and for pruning trees and shrubbery,and in particular it relates to such devices that are hand operated.

An object of this invention is to provide an improved pruning tool whichis lightweight and simple in construction and operation.

Another object is to provide such a tool which can With ease cut throughrelatively large and tough tree limbs.

In cutting tree limbs or shrubs which are high or difficult to reach itis desirable to have a quick acting, onestroke cutting tool which is socompact and light-weight that it can be mounted on a long extension polewithout becoming unwieldy. It thus may be brought within cuttingdistance of remote or lofty limbs by an operator standing on the ground.However, in the past, such cutting tools were of such low power thatthey were not much help or else they were complicated, bulky, and/orexpensive. The present invention therefore seeks to provide a highpower, lightweight and inexpensive pruning tool.

In accordance with the present invention, in one specific embodimentthereof, an improved hydraulic cylinder of long, thin configuration isbuilt into the frame of a cutting tool and controlled by a relativelylight hand pull to exert a tremendous pressure on a knife blade to moveit against an anvil in the process of cutting a limb or the like.Because of the advantageous arrangement of the parts of this tool, aminimum number of parts is needed and these are simple and easilyassembled. Accordingly the tool is lightweight and inexpensive.

A more complete appreciation of the many advantages of this inventiontogether with a better understanding of its general nature will best begained from a study of the following description given in connectionwith the accompanying drawings in which:

Figure 1 is a longitudinal sectional view of the top part of a cuttingtool embodying features of the present invention, showing the knifeblade and anvil together with the upper portion of the hydrauliccylinder;

Figure 2 is a longitudinal sectional view of the middle part of thetool, showing the lower part of the hydraulic cylinder and the handoperated mechanism for controlling the cylinder;

Figure 3 is a side elevational view of the bottom part of the tool; and

Figure 4 is a longitudinal sectional view of the top part of the tooltaken on the lines 44 in Figure 1.

Figure 1 shows the head 11 of a cutting tool 10 having a long tubularframe 12 which extends the length of the tool. Head 11 consists of ananvil 14 screwed to the top end of the frame and a knife blade 16adapted to move along the axis of the frame toward and away from thelimb supporting surface 17 of the anvil. (Blade 16 is shown advancedinto contact with surface 17.) This blade is fixed by means of screw 18and plug 19 (see Figure 4) to a hollow cylinder 20 which fits slidablywithin the end part of frame 12 and forms the piston for the hydraulicchamber 22. Fluid within this chamber is prevented from leaking throughor past cylinder 20 by a plug 24 which carries a sealing ring 25. Plug24 is force fitted into the lower end of the cylinder 20 and supports atits inner end a compression spring 26. The other end of this springpushes against pin 28 which passes through two slots 30 in cylinder 20and through frame 12 and the lower part of anvil 14, the pin beingsecurely fixed to these last two members. Thus when the pressure inchamber 22 is released, spring 26 pushes cylinder 20 downward andretracts blade 16 from anvil 14. Cylinder 20 and blade 16 are kept inalignment with anvil 14 by this pin 28 riding in slots 30.

Fluid pressure within chamber 22 is raised by the advance upward ofplunger 32. This plunger is a solid rod having a diameter substantiallyless than the diameter of chamber 22 and a length great enough so thatwhen moved into chamber 22, blade 16 can advance from its back limitinto contact with surface 17.

As seen in Figure 2, the lower part of plunger 32 passes through thecenter of the neck portion 34 of a housing 36 which is tightly andfirmly fitted within the end of frame 12. Sealing rings 37 and 38prevent leakage of fluid from chamber 22 through or around shoulder 34.Housing 36 receives and tightly grips the end of tube 13 which serves asa continuation of frame 12. A filler plug 39 screwed through the wall offrame 12 provides a simple means of filling chamber 22 with a suitablehydraulic fluid.

The bottom end of rod 32 is bifurcated and carries a pulley 41) aroundwhich rope 42 passes. One end of the portion of this rope passing aroundpulley 40 is attached by means of a bushing assembly 44, having matinginner and outer sleeves and extending through housing 36 and tube 13, tothe frame of the tool. The other end of the rope passes around a secondpulley 46 which is mounted on housing 36. As seen in Figure 3, this endof the rope continues outside the tube 13 to an anchor point 47 near thebottom end of the tube to which, for convenience, it is afiixed. Ahandle 48 which provides a grip for the operators hand is attached tothe rope at a suitable place above point 47. The bottom end of tube 13is fiared to permit the insertion of a like diameter extension arm ifdesired.

By pulling down on rope 42, rod 32 is pushed upward into chamber 22 andas it advances, because of the pressure exerted on plug 24, cylinder 20is forced upward. In this movement, for each 1" upward advance of rod32, rope 42, because of the arrangement of pulleys 40 and 46, must movedownward 2", i. e. twice the distance rod 32 moves. The volume ofchamber 22 remains substantially constant, however, and therefore agiven pull on rope 42 is translated into a force twice (this factor oftwo resulting from the ratio of movement of rope 42 to rod 32) the ratioof the cross-sectional area of plug 24 to the crosssectional area of rod32. Thus, for the parts of tool 10 proportioned as shown, a 50 poundpull on rope 42 becomes approximately a half ton force pushing knife 16against anvil 14. When the pull on rope 42 is released, spring 26 actsto return knife 16 to its back position in which the tool is ready tomake another cut.

In the above described embodiment frame 12 can, if desired, be made ofone continuous length of tubing instead of being formed from two lengthsas shown. In addition to this change other changes or modifications mayoccur to those skilled in the art and these changes and/ ormodifications can be made without departing from the spirit or scope ofthe invention as set forth.

I claim:

1. A pruning tool comprising an elongated tube a portion of whose insidevolume forms the chamber of a hydraulic cylinder, a piston slidablewithin said hydraulic cylinder and projecting through the upper endthereof, a knife blade carried by said piston, an anvil support opposingsaid knife blade and fixed to the upper end of said tube, and a rodslidable into the chamber of the cylinder from the outside thereofthrough the lower end thereof to create in said cylinder a pressuresufficient to move said piston and said knife blade toward said anvilsupport.

2. The combination of elements as in claim 1 in which said rod movesinto the chamber in a direction substantially parallel to the axis ofsaid tube and carries on its outer end a rope and pulley lift by whichit can be advanced into the chamber.

3. A light, hand-operated pruning tool comprising a tube a portion ofwhose inside volume is adapted to be the liquid filled chamber of ahydraulic cylinder, a piston slidable inside the upper end of said tubeand forming a movable part of the hydraulic cylinder, a knife bladeadapted to be moved by said piston, a member opposite said knife bladefor holding in conjunction with said blade an object for cutting, meansincluding a spring for retracting said knife from said member, meansincluding a constriction in said tube spaced a distance from the upperend thereof to make the cylinder liquid-tight, and means including athin rod-like member slidable into the chamber of the cylinder from theoutside thereof through said constriction to move said piston, theamount of liquid in said chamber remaining constant throughout thismovement.

4. The combination of elements as in claim 3 in which said memberopposite said knife blade is fixed to said tube, said means including aspring for retracting also includes a pin fixed to said tube, and oneend of said spring pushes against this pin and the other pushes againstsaid piston.

5. In a light hand-operated pruning tool having a long thin frame, acutting head comprising: a hollow core piston slidable axially in theend of the frame and forming a movable part and the upper end seal of ahydraulic cylinder within the frame, a knife blade carried by saidpiston, an anvil fixed to the frame and having a supporting surfaceacross the line of advance of said blade, a pin fixed to the frame andpassing through an elongated slot in said piston, and a compressionspring within the hollow core of said piston pushing against said pinand against said piston to move said blade away from said anvilsupporting surface.

6. In a light hand-operated pruning tool having a cutting head, atubular frame, a piston slidable in the upper end of said frame andforming a movable part and the upper end seal of a hydraulic cylinderextending along an inside portion of the length of said frame, aconstriction spaced within said frame a distance below the upper endthereof and forming a portion of the bottom end seal of the hydrauliccylinder, a thin rod-like member movable within said frame along theaxis thereof through said constriction into and out of the hydrauliccylinder, handactuated means including a low friction member carried onthe end of said rod-like member a low friction member carried by saidframe and a flexible cord engaging said low friction members for movingsaid rod-like member into the hydraulic cylinder thereby to actuate thecutting head of said tool, the volume of the hydraulic cylinderremaining substantially constant.

7. The combination of elements as in claim 6 in which said low frictionmembers are pulleys, and said flexible cord is fixed to said frame atone end, passes around said pulley carried by said rod-like member, thenaround said pulley carried by said frame, thence along the outside ofsaid frame where it is adapted to be pulled by an operator of said tool.

8. The combination of elements as in claim 6 in which said constrictionis an annular plug with a small central opening and is tightly fittedwithin said frame, and said rod-like member is slidable through thesmall central opening farther into or farther out of the hydrauliccylinder.

9. The combination of elements as in claim 8 in which said annular plugis an integral part of a housing fixed to said frame, and said frame isin two pieces joined together by said housing.

10. A pruning tool comprising a tubular frame, a hollow core pistonslidable in the upper end of said frame and forming a movable part andthe upper end seal of a hydraulic cylinder extending along an insideportion of the length of said frame, a housing having an integral neckportion fitted within the inside of the lower end of said frame saidneck portion having a small opening parallel to the axis of said frame,a knife blade carried by said piston, an anvil fixed to the upper end ofsaid frame and having a surface across the line of advance of saidblade, a pin fixed to said frame and passing through a pair of elongatedslots in said piston, a compression spring within the hollow core ofsaid piston pushing against said pin and against said piston to movesaid blade away from said anvil surface, an extension mem-,

ber fitted within said housing along the axis of said frame and forminga continuation thereof, a thin rod slidable within said extension memberthrough the opening in said neck portion farther into and farther out ofthe hydraulic cylinder, at first pulley carried on the end of said rod,a second pulley carried by said housing, and a rope attached to a fixedpoint at a place above said first pulley and passing down around saidfirst pulley, up and around said second pulley and down the outside ofsaid extension member.

No references cited.

